Manually actuated valve assembly



Oct. 29, 1968 D. VOLKMANN 3,408,039

MANUALLY ACTUATED VALVE ASSEMBLY Filed Feb. 4, 1966 //VVEN70,P D/E'TEA VOL/(MANN Q 454%, WZ%M United States Patent Claims. of. 251-237 ABSTRACT OF THE DISCLOSURE An air-operated fastener driving tool or the like is provided with an improved manually operable control valve assembly including a valve chamber mounted in the casing of the tool, a valve stem movably mounted in the valve chamber, and a trigger mounted on the casing and engageable with the lower end of the valve stem. The valve stem is normally urged by air pressure to its inoperative position and is shiftable by the trigger to its operative position. Movement of the valve stem to its inoperative position is limited solely by a support disc aflixed to the upper end of the valve stem and engageable with a shoulder on the valve chamber. Thus, the normal inoperative position of the valve stem is fixed independently of manufacturing tolerances associated with the trigger or the casing or the mounting of the valve chamber in the casing.

The present invention relates to a manually actuated valve assembly, and more particularly to a control valve for an air-operated device, for instance a hand tool for driving fasteners, such as staples, nails, pins and the like, into a work. :In devices of this type, the air inlet valve introducing air under pressure to a cylinder must be instantly opened so that the piston, which is guided within the cylinder, during the short time of its working stroke, is immediately activated by the air under full pressure. Since the air inlet valve is required to have a large flow section, only a strength in excess of the power of a human operators finger is able to open it immediately. Therefore, the air inlet valve is pneumatically controlled by a manually actuated control valve which works as a servo valve and only requires little finger force to be released. This control valve is provided with a stem, which carries the valve elements. This stem is guided in a valve chamber and is moved by a trigger lever arranged at its free end. The valve stem often is provided with an annular face which is under the effect of the compressed air which presses the valve on its seat into closed position.

In constructions of these valves which are known in the art, the travel of the stem and accordingly opening and closing of the control valve which is arranged in the air supply duct of the cylinder, depends on the tolerances prevailing at the point where the trigger lever is mounted on the casing of the device, inside the casing itself and between the latter and the valve chamber inserted into it. As the valve chamber is usually screwed into a threaded bore of the casing, substantial tolerances may occur between both these parts which add to the tolerances of the bearing of the trigger lever. These tolerances are further enlarged by the gear ratio of the trigger lever. They can develop to be so great that the trigger lever may abut the casing of the device without actuating the valve. As any single device of a manufacturing series has its individual tolerances the travel of the stem of the control valve which is necessary for a working stroke of the piston varies within a larger manufacturing series from one device to another, which 'ice circumstance causes further difiiculty in the use of these devices.

The object of the present invention is to provide a valve assembly in which a like travel of the valve stem in all the devices, independently of the manufacturing tolerances, is obtained without increasing the manufacturing cost by too much precision. According to the invention a supporting element is attached to the valve stem in order to support it on the valve chamber. Advantageously, an annular disc is fastened to a shoulder on the end of the stem and abuts a corresponding surface of the valve chamber. By this construction, the valve stem is neither supported on the trigger leveras has been the case with the conventional constructionsnor on a supporting surface of the casing, which results in elimination of the tolerances of these parts.

Another object of the invention is to provide a valve assembly in which the differences in the stroke of the valve stem which so far have been caused by the tolerances are entirely eliminated. Since the stem is only supported on the valve chamber, any play which may occur between its free end and the trigger lever does not have any influence on the effective stroke of the valve stem and on the release of the working stroke of the device.

When the device is in operation the stem of the control valve is kept in its closed position by the air admitted to its annular surface. If the device is separated from the air supply for carrying out a repair or during transport, the valve stem can freely move in the cylindrical bore of the valve chamber and can fall out when the device is turned over. It is therefore a further object of the invention to provide means which are inserted into the valve chamber and which limit the movement of the valve stem. These means preferably consist of a stop or spring ring, which is mounted above the annular surface supporting the valve stem and has an inside diameter smaller than the outside diameter of the annular disc of the valve stem. This stop is only effective as long as the device is not connected to a pneumatic air supply; it is not effective during normal operation because it is not reached by the stroke of the valve stem.

Other and further important objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawings, in which drawings the invention, for purposes of illustration, is shown as applied to a portable pneumatic stapler.

In the drawings FIG. 1 is a partial longitudinal section of the control valve of a portable air-operated device, and

FIG. 2 is a part of FIG. 1 in an enlarged scale.

With reference to the drawings, the casing 1 of an airoperated staple driving device contains an air chamber 2 which is in permanent communication with an air admission pipe (not shown) and which may via a manually operated control valve be connected with the working cylinder, which contains a striking piston and is not shown in the drawing. The control valve consists of a valve chamber 3 which is inserted into a bore 4 of the casing 1 having a plurality of steps and with its middle portion 5 is screwed to casing 1. The lower portion 6 of the valve chamber is sealed against the casing 1 by a resilient O-ring 7.' The valve chamber 3 is provided with a cylindrical bore 8, in which the valve stem 9 of the control valve is movably guided with play in nearly vertical direction. In its upper portion, valve stem 9 carries the two valve seals 10 and 11, which consist of resilient O-rings and are arranged in corresponding annular grooves 12 and 13 of stem 9. In the initial position represented in the drawings, sealing ring 10 abuts the inside Wall of valve bore 8, closing the latter, while the lower sealing ring 11 is outside valve bore 8.

The valve stem 9 crosses the air chamber 2, and its lower portion is of a larger diameter than its upper portion. At the point of transition, an annular surface 25 is formed to which the compressed air from within chamber 2 is admitted to press the valve stem into its closed position. In this position, the lower end of valve stem 9 is situated at a small distance from the trigger lever 15 which is pivotally mounted on a pin 14 located on casing 1 so that movement of the trigger lever 15 effects movement of the stem 9 from its closed position to its open or operative position in which the lower valve seal 11 is closely adjacent to the internal wall of valve bore 8 and the upper valve sealing is placed above bore 8 of valve chamber 3.

In order that the stroke of valve stem 9, which starts the working stroke of the device, may be independent of the tolerance of the bearing of trigger lever on pin 14, of the tolerance of valve chamber 3 against the casing 1 and of the tolerances of the casing 1 itself, the valve stem 9 is according to the invention supported solely on the valve chamber 3, and this is done by means of a supporting member in the shape of an annular disc 16 which is secured to the upper, stepped end 17 of stem 9 and is by an adapter sleeve 18 or another fastening element clamped tightly against the shoulder of stem 9. The annular disc 16 is of a larger diameter than the valve stem 9 and abuts an annular surface 19, which is contained in the upper portion of valve chamber 3 and forms the lower limitation of a cylindrical recess 20 in the upper portion of valve chamber 3. The axial length of the cylindrical recess 20 is slightly larger than the operating stroke of valve stem 9. So as to prevent the stem 9 from falling out of the casing 1 as the device is turned over after it has been separated from the air admission pipe, a safety ring 21 is imbedded in the cylindrical recess 20, which ring is for instance a spring ring having an internal diameter smaller than the external diameter of the annular disc 16. If the stem 9 is to be dismounted, for instance for replacing its seal rings 10 and 11, this is possible without any difiiculty after safety ring 21 has been removed.

In its center part, the valve chamber 3 is provided with a port 22 which communicates with a passage 23 within the casing 1. This passage 23 extends, for instance, to the upper side of the piston of an air-operated valve (not shown) which is used as an air inlet valve for the working cylinder. 7

In its initial position shown in the drawing, the passage 23 is via the port 22 and the annular clearance between valve stem 9 and the bore 8 of valve chamber 3 and also via the bore 26 of the casing 1 in open communication with the air chamber 2 so that the inlet valve (not shown) is pressed on its seat by the compressed air and interrupts the introduction of compressed air to the working cylinder.

When the stem 9 is raised into its operative position by squeezing the trigger 15, the sealing ring 11 is caused to abut the internal wall of valve bore 8 and blocks the admission of compressed air from the air chamber 2 via passage 23 to the inlet valve (not shown) to the working cylinder. The upper sealing ring 10 is then situated above the annular surface 19 of the valve chamber so that the passage 23 is via the cylindrical recess 20 in open communication with the external air. The upper side of the inlet valve (not shown) is thereby exhausted and is by pneumatic force raised in a well-known manner into its operating position, in which the air chamber 2 '4 receives a direct open communication with the working cylinder.

The construction of the valve according to the invention may not only be used in control valves of airoperated devices, but also in other cases.

Although the invention is herein shown and described as applied to a portable pneumatic stapler, it is to be understood that in its broadest aspect the invention is not to be so limited except as particularly set forth in the following claims.

I claim:

1. In an air-operated device of the class described having a casing and manually operable trigger means mounted on the outside of said casing for actuating a control valve, the improvement which comprises a valve chamber mounted in said casing, a control valve including an elongated valve stem having a valve portion intermediate the opposite end portions of said valve stem and movably disposed in said valve chamber for movement between operative and inoperative positions, sealing means cooperable with said valve portion and said valve chamber for controlling the passage of air through said valve chamber, rigid support means secured to one end portion of said valve stem in spaced relation from said sealing means, and shoulder means on saidvalve chamber engageable by said support means for limiting the movement of said valve pOrtiOn from its operative position to its inoperative position, the opposite end portion of said valve stem extending outside of said casing and being engageable by said trigger means for effecting movement of said valve portion from its inoperative position to its operative position.

2. The device of claim 1 further characterized in that said valve chamber has an elongated cylindrical bore and said sealing means comprises a pair of sealing elements carried on said valve portion and movable into and out of the opposite ends of said cylindrical bore upon movement of said valve stem.

3. The device of claim 1 further characterized in that said valve stem has an intermediate annular face adapted to be acted upon by air pressure within said casing for normally urging said valve portion into its inoperative position.

4. The device of claim 1 further characterized in that said support means comprises a rigid annular disc detachably afiixed to said one end portion of said valve stem.

5. The device of claim 1 further characterized in that said valve chamber has an inwardly extending axial recess, said shoulder means defining the inner end of said recess, and removable stop means is provided adjacent the outer end of said recess which is cooperable with said support means for preventing inadvertent removal of said valve stem from said valve chamber.

References Cited UNITED STATES PATENTS 279,887 6/ 1883 Stitzel 137-625.69 2,800,798 7/1957 Korsmo 251-233 X 2,854,998 10/1958 MacGlashan et al.

l37-625.69 X 3,269,274 8/1966 Lingle et a1. 137625.26- X 3,323,602 6/1967 Lysell 137--625.26 X

' WILLIAM F. ODEA, Primary Examiner.

D. R. MATTHEWS, Assistant Examiner. 

